Regulation of cell proliferation by programmed cell death (apoptosis) maintains tissue homeostasis during development and differentiation (Raff, M. D., Nature (1992) 356:397-400; Vaux, D. L. et al., Cell (1994) 76:777-779). This process involves an evolutionarily conserved multi-step cascade (Oltvai, Z. et al., Cell (1994) 79:189-192), and is controlled by proteins that promote or counteract apoptotic cell death. Apoptosis also involves cell surface receptors (Smith, A. et al., Cell (1994) 76, 959-962), and associated signal transducers (Tartaglia, L. A. et al., Immunol Today (1992) 13:151-153), protease gene families (Martin, S. L. et al., Cell (1995) 82:349-352), intracellular second messengers (Kroemer, G. et al., FASEB J (1995) 9:1277-1287), tumor suppressor genes (Haffner, R. et al., Curr Op Gen Dev (1995) 5:84-90), and negative regulatory proteins that counteract apoptotic cell death (Hockenbery, D. et al., Nature (1990) 348:334-336). Aberrantly increased apoptosis or abnormally prolonged cell survival (Oltvai, Z. N. et al., Cell (1994) 79:189-192) may both contribute to the pathogenesis of human diseases, including autoimmune disorders, neurodegenerative processes, and cancer (Steller, H., Science (1995) 267:1445-1449; Thompson, C. B., Science (1995) 267:1456-1462).
Specifically, for example, inhibitors of apoptosis, most notably of the bcl-2 family (Reed, J, J Cell Biol (1994) 124:1-6, and Yang, E, et al., Blood (1996) 88:386-401), maintain lymphoid homeostasis and morphogenesis in adult (Hockenbery, D et al., Proc Natl Acad Sci USA (1991) 88:6961-6965) and fetal (LeBrun, D. et al. (1993) 142:743-753) tissues. Deregulated expression of bcl-2 has also been implicated in cancer, by aberrantly prolonging cell survival and facilitating the insurgence of transforming mutations.
In addition to bcl-2, several members of a new gene family of inhibitors of apoptosis related to the baculovirus IAP gene (Birnbaum, M. J. et al., J Virology (1994) 68:2521-2528; Clem, R. J. et al., Mol Cell Biol (1994) 14:5212-5222) have been identified in Drosophila and mammalian cells (Duckett, C. S. et al., EMBO J (1996) 15:2685-2694; Hay, B. A. et al., Cell (1995) 83:1253-1262; Liston, P. et al., Nature (1996) 379:349-353; Rothe, M. et al., Cell (1995) 83:1243-1252; Roy, N. et al., Cell (1995) 80:167-178). These molecules are highly conserved evolutionarily; they share a similar architecture organized in two or three approximately 70 amino acid amino terminus Cys/His baculovirus IAP repeats (BIR) and by a carboxy terminus zinc-binding domain, designated RING finger (Duckett, C. S. et al., EMBO J (1996) 15:2685-2694; Hay, B. A. et al., Cell (1995) 83:1253-1262; Liston, P. et al., Nature (1996) 379:349-353; Rothe, M. et al., Cell (1995) 83:1243-1252; Roy, N. et al., Cell (1995) 80:167-178). Recombinant expression of IAP proteins blocks apoptosis induced by various stimuli in vitro (Duckett, C. S. et al., EMBO J (1996) 15:2685-2694; Liston, P. et al., Nature (1996) 379:349-353), and promotes abnormally prolonged cell survival in the developmentally-regulated model of the Drosophila eye, in vivo (Hay, B. A. et al., Cell (1995) 83:1253-1262). Finally, deletions in a IAP neuronal inhibitor of apoptosis, NAIP, were reported in 75% of patients with spinal muscular atrophy, thus suggesting a potential role of this gene family in human diseases (Roy, N. et al., Cell (1995) 80:167-178).
Therapeutic and diagnostic uses of nucleic acids that encode various inhibitors of apoptosis relating to a member of the IAP family have been described in the patent literature. See, for example, International Patent Applications No. WO 97/06255, WO 97/26331, and WO 97/32601. In particular, the uses of such genes and gene products are contemplated for the novel protein and its encoding nucleic acid discussed below.
Recently, a novel gene encoding a structurally unique IAP apoptosis inhibitor, designated Survivin has been identified. Survivin is a −16.5 kD cytoplasmic protein containing a single BIR, and a highly charged carboxyl-terminus coiled-coil region instead of a RING finger, which inhibits apoptosis induced by growth factor (IL-3) withdrawal when transferred in B cell precursors (Ambrosini, G. et al., Nature Med. (1997) 3:917-921). At variance with bcl-2 or other IAP proteins, Survivin is undetectable in adult tissues, but becomes prominently expressed in all the most common human cancers of lung, colon, breast, pancreas, and prostate, and in −50% of high-grade non-Hodgkin's lymphomas, in vivo. Intriguingly, the coding strand of the Survivin gene was highly homologous to the sequence of Effector cell Protease Receptor-1 (EPR-1) (Altieri, D. C., FASEB J (1995) 9:860-865), but oriented in the opposite direction, thus suggesting the existence of two separate genes duplicated in a head-to-head configuration.
The present invention is based on the identification of a novel human gene which is nearly identical to EPR-1, but oriented in the opposite direction. The antisense EPR-1 gene product, designated Survivin, is a distantly related member of the IAP family of inhibitors of apoptosis (Duckett, C. S. et al., EMBO J (1996) 15:2685-2694; Hay, B. A. et al., Cell (1995) 83:1253-1262; Liston, P. et al., Nature (1996) 379:349-353; Rothe, M. et al., Cell (1995) 83:1243-1252; Roy, N. et al., Cell (1995) 80:167-178), and is prominently expressed in actively proliferating transformed cells and in common human cancers, in vivo, but not in adjacent normal cells. Functionally, inhibition of Survivin expression by up-regulating its natural antisense EPR-1 transcript resulted in massive apoptosis and decreased cell growth.